JPH04505140A - Land vehicle suspension control system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Land vehicle suspension control system Technical field The present invention relates to a land vehicle suspension control system.

Background technology "land vehicle" means a vehicle adapted for movement on a road surface in contact with the ground; , such as automobiles, motorcycles, tractors, track vehicles, etc.

In particular, the present invention provides a land vehicle suspension system for a land vehicle having an active suspension device. Regarding pension control systems.

Active suspension systems receive commands from a microprocessor, for example. The actuator that corrects, changes, or controls the vehicle posture depending on the Suspension that suspends or substitutes general suspension parts such as suspension parts such as suspension parts such as suspension parts such as suspension parts such as suspension parts such as suspension parts such as suspension parts such as dampers or suspension parts. It is an application device. This type of active suspension system reduces the force exerted on the vehicle body. The aim is to minimize variations, improve vehicle safety and improve driver safety. The aim is to increase the comfort of passengers.

The command signals that control the actuators typically include multiple variables that determine the vehicle's attitude. generated based on measured values. In actual active suspension system control the actuator according to the previously measured change in the value of the variable. For example, by tilting the vehicle attitude, a given steady state or dynamic The actuator can be used to cancel the influence of the load or to anticipate the expected road surface conditions. It is possible to control the data.

Active suspension systems are common. For example, EP-A-0 114757, each wheel/hub assembly (I(UB) ASSEMBLY) Forces are measured and processed at support points in the vehicle body and transferred between each wheel/hub assembly and the vehicle body. For four-wheeled vehicles that provide the necessary output to the actuator installed to An active suspension device is disclosed.

(pitch), ti swing (roll), twist (warp)) By this, it is possible to control the attitude of the vehicle and maintain the desired attitude of the vehicle. The actuator output required to cancel the compound mode force is calculated in order to .

According to such an active suspension system, the suspension of the vehicle By continuously changing the characteristics, it is possible to adapt to various road conditions and/or vehicle operation. It has the great advantage of being able to adapt to changing conditions. active suspension Compared to vehicles without a suspension system, the contact between the wheels and the ground is greater. It also makes vehicle behavior more predictable for the driver. Therefore, cars with advanced safety characteristics by using active suspension. It becomes possible to manufacture both.

However, in existing active suspension systems, the microprocessor used between the vehicle body and the wheel/hub assembly to apply force at the command of the sensor. This is because the actuator accurately executes the command signals from the microprocessor. The problem is that it is incomplete. For example, an actuator that receives a command signal There is a gap between the tuator and the piston of the actuator that operates in response to the command signal. There is always a finite time delay.

The controls of active suspension systems operate very quickly, so e.g. For example, a delay in actuator movement based on the first command from a microprocessor. Such a time delay is unacceptable because it may interfere with the execution of the next command.

The output from the actuator of an active suspension system is interposing an isolator block made of rubber or other material between the data and the vehicle body. This makes it smoother. With such an isolator, loads exceeding a specified value can be avoided. This makes it possible to convey information.

However, due to the intervention of the isolator, it is difficult to detect loads that move the vehicle body. The active suspension system does not respond to A collision occurs. This is because the isolator isolates the load from the system's load cells. It is used to sense loads acting on actuators and isolators. It is set up for the purpose of In this way, the isolator is used for active suspension The suspension system operates as an independent passive suspension system, ensuring that the vehicle remains stationary. or provide some freedom in the load path between the road surface and the vehicle body at the point of movement. Ru.

The isolator receives the load that needs to be measured from the actuator load cell. When separated, accurate feedback measurement of said actuator in response to the demand signal is possible. Since it is difficult to It has heretofore been impossible to accurately control the extension of the actuator.

Disclosure of invention The land vehicle suspension control device according to the present invention is characterized by the fact that the sprung mass of the vehicle and the A means of measuring the force acting between the sprung masses and a signal proportional to the measured load. the vehicle's attitude by applying a correction force based on the signal. actuator means operable to control, the actuator means operable to control; , canceling the loads acting on the entire vehicle body, including the loads separated from the force measuring means. It is characterized by being able to perform stable operation as shown in FIG.

Brief description of the drawing Embodiments of the present invention will be described with reference to the drawings.

Figure 1 shows the vertical sway of the vehicle body without an active suspension device. Schematic diagram showing the influence of forces, Figure 2 shows the vertical vibration of the vehicle body without an active suspension system. Schematic diagram showing the effect of sliding force, Figure 3 shows the rolling motion of the vehicle body without an active suspension system. Schematic diagram showing the effect of sliding force, Figure 4 shows screws in the body of a vehicle not equipped with an active suspension system. A schematic diagram showing the effect of 5 is a schematic front view of a vehicle equipped with a control device according to the present invention, and FIG. 6 is a schematic front view of a vehicle equipped with a control device according to the present invention. FIG.

Detailed description of the invention jf! 1 to 4 show a sprung mass in the form of a vehicle body 20 and four sprung masses, namely four wheels 10.11.12.13 and an interconnected wheel suspension. 1 shows a schematic diagram of a vehicle that is comprised of a motion device (not shown). In the vehicle body 20, It includes all engines, transmissions, and automobile auxiliary parts.

Figures 4 to 4 show the effects of the vehicle body 3 caused by vertical shaking, pitching, rolling, and torsional forces. FIG. 2 is a schematic diagram of a typical displacement state of 0; In Figures 1 to 4, the front left wheel is 10 , the front right wheel is represented by 11, the rear left wheel is represented by 12, and the rear right wheel is represented by 13. Ru. Vertical, vertical, horizontal, and torsional forces are indicated by arrows H, P, R, and W, respectively. has been done. The modal forces in Figures 1 to 4 are indicated by the conventional reference symbols. It is shown that it is acting in the positive direction. The front of the vehicle is marked 21 and the rear is marked 22. has been done.

In Figure 1, the force in the up-and-down mode is the vehicle body on the wheels 10.11.12,]3'' 20 is a downward force of equal magnitude acting on the four points supporting the The body moves downward evenly without leaning in any direction due to the influence of positive up-and-down motion. .

A positive pitch mode force is illustrated in FIG. Due to the shaking mode force, the front end 21 of the vehicle body is displaced downward without shaking sideways, and It is shown that the rear part 22 of the vehicle body is displaced upward from the initial position and becomes easily X.

FIG. 3 shows a positive roll mode force, in which the left side of the vehicle body 20 is tilted downward or The right side of the vehicle is displaced upward, and the vehicle body is tilted about the vertical axis.

FIG. 4 shows the effect of positive torsional forces on the vehicle body 20. Torsional force is rectangular In the case of a car body, there is usually one pair of diagonal corners of the car body 20 and one other diagonal corner. This is to displace the pair in each direction.

The codes used here indicate that the front left and rear right corners of the vehicle have positive values. or is displaced downward by warping force.

Let's consider the forces that the car body receives, which can be broken down into modal forces, by classifying them into three categories. It's easy to understand. The static load on a vehicle is the mass of one vehicle when the vehicle is stationary. It is the reaction force required to support the cargo/passenger load.

Steady state loads on a moving vehicle include steering angle, vehicle speed, and vehicle acceleration. / Determined from the values of vehicle movement variables such as deceleration.

The dynamic load of the vehicle is determined by the road information J (road 1nput), It is impossible for the driver to predict this. Such dynamic loads are e.g. This occurs when wind affects the vehicle or when the wheels hit a bump on the ground.

FIG. 5 shows a schematic front view of an automobile equipped with a control device according to the present invention. .

A car has four wheels, 10.11 of which are illustrated in Figure 5. , each supported by a hub assembly (not shown). Hub assembly shown The axle part is rotatably fixed to the end of the vehicle body in the 20 direction from the wheel. It is supported by AXLE MEMBER 18.

The vehicle is equipped with an active suspension system. active suspension The engine device receives commands from a microprocessor 31 attached to the vehicle body 20. According to the number, each is installed so that it operates between the axle member 18 and the vehicle body 20.

It is composed of four double-acting hydraulic actuators 14. Each actuator The rod 17 of the rod 14 is rotatably fixed to the connected axle member 18. .

Each hydraulic actuator] 4 is a pump and a reservoir (not shown), like conventional hydraulic components. It has a pair of fluid supply lines 15 connected to (shown). Each actuator 14 The flow of hydraulic fluid in and out of the is supported by the servo valve control wiring (νIRING) 32. a servo valve 1 which is operated according to a command signal from a microprocessor 31; 6.

The active suspension system shown in Fig. 5 includes each actuator] 4 and the vehicle body. Load cells 25 are included, each arranged to measure the force acting at 20. There is. The signal from the load cell 25 is adjusted by the microprocessor 31 and activated. The evaluator 14 operates to correct the attitude of the vehicle body and to adjust the position of each wheel/hub assembly and the vehicle body. Perform the required amount of damping (DAMPING) between 20 and 20°C. Required body posture and degree of damping is programmed into the microprocessor 31 in advance.

For full control of vehicles using active suspension systems, In addition to the loads acting between each wheel/hub assembly and the vehicle body, there are It has been found necessary to measure and process a large number of variables.

One such variable is the lateral acceleration of the vehicle body 20. For example, a vehicle traveling on a curve The vehicle body 20 is subject to lateral acceleration in a variety of situations, including situations in which: Therefore, as shown in Fig. The vehicle is equipped with a lateral accelerometer 26 installed on the vehicle body 20 near the center of gravity of the vehicle. ing. The lateral accelerometer 26 generates a signal proportional to the lateral acceleration of the vehicle body 20, and The code is sent to microprocessor 31. The code conversion is selected depending on the lateral acceleration. Ru. The arrow ny in FIG. 5 represents the direction of positive lateral acceleration.

When the vehicle body 20 is subjected to lateral acceleration, the load is transferred from one side of the vehicle to the other, which causes rolling force is generated on the vehicle. For example, the wheel 11 and the corresponding car behind the vehicle By driving around a curve of constant radius with the center of the curve somewhere to the left of wheel 13. If the vehicle experiences the constant lateral acceleration ny shown, the load will be at the center of the curve. to the outermost wheels 10 and 12 and at the same time to the innermost wheel 11.1. Stay away from 3. Therefore, the vehicle swings sideways toward the outside of the curve.

The load movement is represented by the force Fny shown in FIG. Fny is the lateral acceleration ny of the vehicle As a result, it represents the vertical load that acts on the vehicle body 20. Therefore, Fny is proportional to ny. Ru. As shown in FIG. When ny acts vertically downward at the corner of , as shown in the figure, wheel 1 It acts vertically upwards at the two corners of the vehicle body 20 adjacent to 0 and 12. follow Therefore, Fny is added to the load reaction on the right side of the vehicle and subtracted on the left side as shown. It will be done.

In fact, Fny has a predetermined distance between the front and rear of the vehicle according to its suspension characteristics. Figure 5 shows the equivalent force Fny reacting at each corner of the vehicle body 20. This is a simplification by assuming that.

Therefore, the following equations apply at the two corners of the front surface shown in FIG.

At the corner adjacent to the wheel 10, Reacted load −Fs+Fny, , , , , 010. , (1) Adjacent to wheel 11 At the corner where Reacted load - Fs - Fny, , , , , , , , (2) At this time, Fs is This is the static load on the vehicle body 20 that is reacted at each corner of the vehicle body 20.

To eliminate the front roll of the car body in the above situation, the reaction determined by equation (1) above is required. The force is applied to the right actuator 14 shown in FIG. 5, and the reaction force determined by equation (2) The microprocessor 31 causes the left actuator 14 in FIG. must be programmed. Apparently this is the rear of vehicle 30 (not shown) But it can be applied as well.

Since the lateral acceleration to which Fny is proportional can be easily measured, the value of Fny can be compensated for in this way. It is convenient to correct. However, actuator 14 and active suspension A connected servo valve 16 currently available in a microprocessor 31 It is impossible to respond quickly to command signals and obtain satisfactory results.

This is primarily due to the finite time required to actuate the actuator valve. .

Therefore, the delay increases the amount of time that actuator 14 and servo valve 16 operate together. delay is present throughout the suspension system, and this system delay causes the entire suspension system to It is good that it does not affect performance.

This corresponds to the stage shown in FIG. 5 fixed between the top of each actuator 14 and the vehicle body 20. This can be easily achieved by using a rubber isolator as shown in Pulling 27. Ru.

The isolator 27 transfers the load to the vehicle body, for example while the valve is open as described above. To operate an actuator 14 within a limited range without transmitting information to the actuator 20. Aku If the movement of the tuator becomes greater than the movement that the isolator should perform, , a corresponding load is transmitted to the vehicle body 20. Therefore, the microprocessor 31 If properly programmed, the actuators needed to correct the vehicle's attitude will The operation of the motor is not transmitted to the vehicle body 20, and the microprocessor 31 is These movements due to the slow response of the tuator and servo valve can also be transmitted. There is no such thing. This provides a satisfactory ride comfort for the vehicle 30.

Due to the effect of the isolator 27 mentioned above, the load on the vehicle body is reduced to the active suspension. is absorbed by the isolator 27 without any response from the control equipment. isolator -27, like traditional suspension components, has a negative impact on vehicle ride comfort and handling. This is clearly the active suspension of the vehicle, as it reacts while giving This defeats the purpose of including the tion device.

of the actuator 14 required to operate vertically downward or vertically upward; Since the expansion is very unstable, it is necessary to correct the results of isolator 27 above. It is not possible to simply expand actuator 14 by the required length. This is the load The expansion performed by the microprocessor 31 is only computed and activated. A filter that determines when the effect of the isolator 27 connected to the isolator 14 is corrected. This is because feedback measurements are not performed either. Therefore, from the measured load the required The technology for calculating the amount of expansion of the actuator and correcting the effect of the isolator 27 is in practice. Not really practical.

Known characteristics of the vehicle and its suspension system using easily measured values of ny The value of Fny is calculated according to the value of Fny, and the actuator 14 is actuated by an amount proportional to the value of Fny. The preferred method is to simply extend . However, the isolator 27 When this method of correcting the effect is carried out on the vehicle's active suspension system, , the ride and handling of the vehicle is again compromised and in this case the microprocessor Correction of isolator 27, which was also requested by suspension setting commanded by 31'' Experience has shown that there is a possibility of conflicts.

To compensate for the effect of the isolator 27, the measured lateral acceleration ny of the vehicle must be It is preferable to directly synthesize the DXny value from the values. DXny is isolator 27 The amount of displacement of the actuator 14 required to correct the lateral acceleration ny “seen” from It is a value. DXny is directly proportional to the value of Fny, but it is automatically set as a displacement request. generated, its calculation and execution is based on the measurements used to correct the attitude of the vehicle body 20. There is no interaction with the calculated load value. Furthermore, the actuator 14 A linear variable induction transducer (LINEARVARIABLE) that measures the actual amount of expansion. INDUcTIVE TR^N5DUCER) (LV IT>28 etc. A displacement error loop, a part of which is illustrated in Fig. 6, using a displacement transducer, Generates an output that can be compared with the calculated value DXny of each actuator 14, and applies the load. It is possible to reliably expand each actuator 14 in the state in which the actuator 14 is

In FIG. 6, the output stage of microprocessor 31 is shown.

Microprocessor 31 has a plurality of input terminals 35 and output terminals 36.

Among them, the terminal 35 receives signals from the load cell 25, lateral accelerometer 26, and LVIT 28. receive. Figure 6 shows one-fourth of the control system for a four-wheeled vehicle, with four actuators. Wiring corresponding to one of the data controllers 14 is shown. The remaining control circuit is This is similar.

In Figure 6, gears of 25°, 26°, and 28° are load cell 25, lateral acceleration A total of 26 signals are sent from the LVID 28, and these signals are adjusted by the signal conditioner 38. After that, it is input to the central processing unit (CPU) 37 of the microprocessor 31. Ru. The CPU performs the necessary actions to correct the vehicle body for the loads caused by lateral acceleration. The displacement amount DXny of the actuator 14 is calculated from these signals.

This value of DXny is the actual actuator position measured by the LVI728. It is compared with the value of the position Xact in a comparator, which is an operational amplifier 39. As a result, The generated displacement error signal is output to the servo valve 16 via the servo valve wiring 32 in an appropriate form. be done. However, the rest of the CPU 37, including correction of the dynamic input to the load cell 25, The output must be combined with the output of operational amplifier 39. Therefore, operational amplification The output of the converter 39 is further adjusted by a signal conditioner 40 to receive the C signal sent on line 42. Dynamic output of PU37 and sum junking (SUMMING JUNCTION) At 41, it becomes possible to add up. The resulting total output is the output terminal 36 and and is sent to the servo valve via the servo valve control wiring 32.

In the above device, the vehicle's lateral acceleration is used to control the actuator. However, other parameters such as yaw angular acceleration may also be used.

The applicant also deals with load cancellation on the vehicle body, for which it was not possible to measure forces.

In that method, a deflection element mounted in series with the actuator The movement of the sprung mass caused by an external force acting on the (passive isolator, etc.) canceled by moving the actuator in the opposite direction according to a given value of force. Ru. The applicant has determined that the Cancellation of external forces acting on the flexural element resulting from mechanical and aerodynamic loads It is aimed at people.

The action required to compensate for the loads applied to the flexure elements in the suspension. The mode operation of the tuator is as follows.

(Xdm)=-('(Kt), ((Fcf)+(Fcs))) At this time, (X d m) is the vector of required mode displacement amount (Fcf) is the vector of inertia force correction (More on this later) (Fcs) is the aerodynamic correction vector (More on this later) (Kt) is the series stiffness element of the mode coordinate (SERIES 5TIFFNES S ELEMENT) (f) f: Depth matrix (FLEXIBILITY MAT l? ]X).

The required movement of the actuator is achieved by converting the mode displacement amount back into actuator coordinates. It can be obtained by

(Xam) = (Txc), (Xdm) At this time, (Xam) is the necessary addition And the average actuator displacement vector (Txc) expresses the displacement of the mode coordinates. Transformation matrix to convert to actuator coordinates.

These are ignored if the aerodynamic loads on the vehicle are expected to be small.

If the geometry of the suspension connection is known and in parallel with the actuator Various types attached in series to the spring (PARALLEL 5PRING) If the stiffness of the deflection element is equal to the component force, the required deflection matrix is The prime can be calculated. Alternatively, the active suspension of the present invention Applying an external force to the sprung mass of the vehicle attached to the device causes the actuator to Deflection (1) Measure the deflection of the sprung mass and further convert the element to mode coordinates By doing so, the elements can be determined experimentally.

The vector of inertia force correction period (Fcf) can be expressed in matrix notation as follows: Ru.

(Fcf)=(rn), (ΦE) At this time, (Fcf) is the inertia force correction vector ('n) of the mode coordinates, which is the inertia correction factor. The matrix of numbers (ΦE) is the transpose of vectors (nx+, nx, ny, Dr). 　X is longitudinal acceleration ny is lateral acceleration Dr is yaw angular acceleration Once the exact geometry of the suspension connections is known, the elements of the inertia correction factor matrix can be It can be calculated. In other words, this is a suspension, not an actuator. Forces transmitted directly to the vehicle body through coupling and actuators for suspension coupling This is when a false load is determined to be transmitted through the . When calculating coefficients, smooth Perform a series of drives of the target active suspension vehicle on a kana surface and make corrections. The correction coefficient matrix is Adjusting the elements is a very effective method. In addition, the effective coefficient is calculated and the vehicle Another option is to automatically adjust them during normal operation.

Free flow of gas over the vehicle when the effective aerodynamic load is caused by a sprung mass Dynamic pressure (FREE STREAM KINE14ATIC PRESSURE) It is preferable to measure the correction period to control the vehicle suspension. will be included. The correction period is as follows.

(Fcs) - ("ae) (Kp) In this case, (Fcs) is the force correction vector (rae) in the mode coordinates, which is the aerodynamic force vector of coefficients Kp is M1 constant vehicle dynamic pressure.

Average measured vertical by wind tunnel test or dynamic pressure when the vehicle is traveling in a straight line Test elements of the aerodynamic coefficient vector from any of the methods of recording changes in load. It can be calculated as follows.

The device of the invention provides stable expansion of the actuator 14 even under load. Although this extension is very flexible in terms of Utilizes individual signals from devices used for overall control of a device or operating device This is possible by using a feedback error loop.

In the above device, a rubber isolator is installed between the actuator and the vehicle body. However, the separation may be effected in other ways and, indeed, due to the inherent nature of the other components of the vehicle. A method based on this may also be used.

Copy and translation of written amendment) Submission (Article 184-8 of the Patent Act) 1. Viewing patent applications PCT/GB90100689 2. Name of the invention Land vehicle suspension control system 3. Patent applicant Address: United Kingdom, Norfolk, N.R. 148 Ezetnowitz Chi Hazel (no street address) Name Group Lotus PLC Representative Monk Tortus John Nationality: United Kingdom 4. Agent August 12, 1991 6. List of attached documents (1) Copy and translation of the written amendment) 1 copy The scope of the claims 1. means for measuring the force acting between the sprung mass of a vehicle and the sprung mass of the vehicle; means for generating a signal proportional to the measured load; and means for generating a signal proportional to the measured load; actuator means connected between the masses and said signal proportional to the measured load; processing and generating a control signal to expand said actuator means and to processing means for contracting to change the position of the sprung mass in proportion to the sprung mass; connected between the sprung mass and the sprung mass, and acts on the sprung mass and the sprung mass; so as to absorb a portion of the force acting on the actuator means generated by the force acting on the actuator means. deformable isolator means, said processing means deforming the measured load signal. The amount of deformation of the isolator means is calculated, and the control signal is corrected to adjust the deformation of the actuator. the actuator means, and in contrast to the deformation of the actuator means, the actuator The isolator may be expanded or contracted to some extent to compensate for deformation of the isolator means. A land vehicle suspension device characterized by:

2. The land vehicle suspension device according to claim 1, wherein the spring quality of the vehicle is said force measuring means for measuring a force acting between said sprung mass of said vehicle; comprising a first means for measuring state load and a second means for measuring dynamic load. , and the signal generating means for generating a signal proportional to the measured load is configured to a first means for generating a signal proportional to the dynamic load; and a first means for generating a signal proportional to the dynamic load. and a second means for configuring.

3. The land vehicle suspension device according to claim 2, wherein the processing means The signal sent to the actuator alone is corrected to compensate for the signal generated by the steady-state load. Correcting the deformation of the isolator means.

4. In the land vehicle suspension device according to claims 1 to 3, the force measuring hand The stage includes means for measuring the aerodynamic load on said sprung mass and is proportional to the measured force. The signal generating means generates a signal proportional to the measured aerodynamic load. further comprising means for generating, the processing means processing a signal proportional to the aerodynamic load; sending a control signal to said actuator means and deforming said isolator means; Conversely, by expanding or contracting the actuator means to some extent, the The deformation of the isolator means due to the aerodynamic load on the upper means is corrected.

5. In the land vehicle suspension device according to claims 1 to 4, the force measuring hand The stage is one or more of the vehicle's longitudinal acceleration, lateral acceleration, yaw angular velocity, and steering angle. means for measuring the top of the vehicle; and measuring the force transmitted between the actuator means and the sprung means. including a load cell.

6. The land vehicle suspension device according to claims 1 to 5 further includes the actuator. means for measuring the length of the eta and means for generating a signal proportional to the length. , the processing means transmits the signal proportional to the length to a closed loop position feedback device. Process with.

7. The land vehicle suspension device according to claims 1 to 6, wherein the isolator -Solution means comprising said actuator means and said sprung means or at least and the at least one isoform, which is a resilient material, and the at least one unsprung means. Consists of raters.

international search report 1--^-, PCT/GB 90100689 International Search Report

Claims (6)

[Claims] 1. means for measuring the force acting between the sprung mass of the vehicle and the unsprung mass of the vehicle; means for generating a signal proportional to the measured load and applying a corrective force based on the signal; actuator means operable to control the attitude of the vehicle by and the actuator means includes a load that is not measured by the force measuring means. It is possible to perform stable operation to cancel out the load acting on the entire vehicle body. A land vehicle suspension device characterized by: 2. The control device according to claim 1 measures acceleration of a vehicle body and means for generating a proportional signal and necessary for canceling the independent loads acting on said vehicle body; means for determining the required magnitude of displacement of the actuator means from the signal; have 3. The control device according to claim 2 includes means for measuring the amount of displacement of the actuator means. and a displacement error loop means, and the measured value of the displacement amount and the judgment value of the displacement amount are is compared by a comparison means and generates an error signal depending on the operation of the actuator means. generate. 4. 4. The control device according to claim 3, wherein the force measuring means, the displacement error loop hand In another aspect, the comparison means is a microprocessor. 5. The control device according to claims 1 to 4 is characterized in that the force measuring means and the sprung mass measurement of the vehicle are including isolator means disposed between the means. 6. The vehicle suspension device disclosed with reference to FIGS. 5 and 6.